1. Field of the Invention:
This invention relates to a vehicle theft deterrent system for protecting the articles in an automotive vehicle, or the automotive vehicle itself, against theft.
2. Description of the Prior Art:
A traditional method of deterring the theft of a vehicle such as an automotive vehicle according to the prior art involves locking the doors, trunk lid and other opening and closing parts of the vehicle by means of a key. However, when the driver and passengers leave the car, a thief may break a window glass and pilfer articles from within the vehicle even though the opening and closing parts have been locked, or the thief may unlock the vehicle by destroying a lock or breaking a window glass, open a door and then use a tool or the like to operate the ignition switch, start the engine and steal the vehicle itself. Thus, the traditional theft deterrent method merely locks the vehicle and does not really deter theft in positive fashion.
Electronic theft deterrent systems that achieve more than the traditional locking method have appeared in recent years. In a typical example of such an electronic theft deterrent system, an "armed phase" is established by closing and locking each opening and closing part of the vehicle, closing the last door and then locking this door without use of a key (so-called "keyless locking", an example of which is locking using a lock button). If someone unlocks or opens any of the opening and closing parts without a key or turns on the ignition switch in the armed phase, an alarm is issued and/or the vehicle is placed in a state in which it cannot travel. Thus, the electronic system does not merely rely upon simple locking but is operatively associated with an alarm to achieve postive theft deterrence. However, if the armed phase is established but then a back door or the like is opened by using a key so that a passenger can retrieve an article from within the vehicle, the armed phase is cancelled and remains cancelled even after the back door is closed. In other words, it is necessary to repeat the keyless locking operation described above.
Japanese Patent Application Laid-Open (KOKAI) No. 60-50052 discloses a theft deterrent system designed to eliminate this inconvenience. Specifically, after the vehicle is placed in the armed phase as by the keyless locking operation, the armed phase is temporarily cancelled for all opening and closing parts of the vehicle if, say, the back door is opened, but the armed phase is restored when the back door closed again.
However, in this proposed system of Japanese Patent Application Laid-Open No. 60-50052 in which the armed phase is cancelled by opening the back door or the like, though it is true that the armed phase is restored when the back door is closed, the vehicle is left defenseless while the back door is open. For example, in order to carry articles from the interior of the vehicle to another place, the driver must leave the vehicle while the back door, say, is left open. There is always the danger that a thief may enter the vehicle while the driver is absent and either pilfer articles from within the vehicle or start the engine and steal the vehicle itself.
Another problem with this prior-art electronic theft deterrent system is that since the armed phase generally is cancelled by use of a key, there is the danger that a thief may forcibly extract a key cylinder from one of the doors to establish a condition similar to that produced by unlocking the door by key, despite the fact that the armed phase has been set. When a door such as a back door is opened under such conditions, the armed phase is cancelled and the vehicle is therefore left unguarded.